use of restrictor plates, need opinions, thoughts?

[Arkie]

I've noticed that in SOME of the dual throat Nikki carb kits and the single barrel Nikkii carb kits that restrictor plates or restrictor gaskets are supplied in addition to the regular gaskets.

I recently installed the restrictor gasket from the kit on a 22 hp Briggs engine using the dual throat Nikki carb and got a good smooth operation.
I knew when doing such that I did not really need the full 22 hp for this lawn tractor with a 42 inch deck when mowing pre-cut lawns.

What are your opinions/thoughts about using the restrictor plates or gaskets so as to reduce amount of air intake to a Briggs engine? The engines I'm working on and testing Nikki carbs have been into previously by Bubba and I do not know if they used restrictors as OEM.

What is a regular rule of thumb for when to use the restrictor gaskets or plate????

[hanz63]

Those are swirl plates. Someone may be able to tell you the when they did this, but I believe they were put there to improve atomization to smooth out the stumble on accel and extra black fuel smoke. Personally I install them, but most folks won't care as long as they have a running mower!

[Arkie]

Those are swirl plates. Someone may be able to tell you the when they did this, but I believe they were put there to improve atomization to smooth out the stumble on accel and extra black fuel smoke. Personally I install them, but most folks won't care as long as they have a running mower!

After your post I stumbled across this link and a picture in the first post of one for a one barrel Nikki. That one is the flat thin steel plate. (no swirls)

The one for the dual throat is just a kinda half moon thick flat gasket and blocks about maybe 1/3 of both of the carb throats between the carb butterfly's and the intake valves input channel. (restricts air flow is why I was using the term restrictor plate)
I suspect that the restriction reduces the HP of the engine as mentioned by the guy in the link.(and allows use of the carb on smaller HP engines and the engine not be running to rich, but I just guessing????????)


Hanz63: Is the picture in this link what you are calling a swirl plate???
I've seen this one barrel plate at this link as usually thin flat metal about .010 thick or as a gasket about .030 thick.

https://www.lawnmowerforum.com/threads/ ... ket.38455/

[hanz63]

No, but that has a purpose too. I'd have to think about documentation on them for the Intek twins. Service school maybe? It would be a long time ago. I just walked in and took a nap, so this is me waling up for now. In this strange link below, the metal plate on the RH side is the swirl plate. Meanwhile, I'll keep my thinking cap on.
https://www.fruugo.co.il/carburetor-for ... nguage=en#

[hanz63]

Closer than I thought. Briggs bulletin 731 from '05.
TO: ALL AUTHORIZED SERVICE ACCOUNTS No: 731
SUBJECT: Smoke Under Initial Load – Swirl Plate Kit 791677 DATE: 10/05
MODELS: Intek V-Twins with 2-Barrel Plastic Intake Manifold – FILE IN: Bulletin
Built Before Date Code 050606xx Binder
CONDITIONS:
Black smoke from exhaust when engine is placed under load after idling for a short time. Noticeable in colder weather,
but not generally experienced above 60-65 degrees F. This does not affect overall engine performance or durability.
POSSIBLE CAUSES:
Insufficient fuel atomization through plastic manifold during idle.
INSPECTION / REPAIR ACTIONS:
Install Swirl Plate Kit p/n 791677 between the carburetor and intake manifold according to the instructions provided in
the kit. The swirl plate improves fuel atomization at idle speed to prevent the smoking condition when load is applied.
WARRANTY:
Normal warranty guidelines apply. This repair procedure will typically take 1 hour to complete.
BRIGGS & STRATTON CORPORATION
Distribution Sales & Customer Support

[KE4AVB]

Tnx for the info hanz63. I created a PDF based on your posted info and filed it in the Briggs download for future reference. I got a couple old Briggs binders and if I find the actual bulletin I will scan and update the file.

[Arkie]

The dual throat Nikki's on the Briggs Intek twins I've been into always had that swirl plate so I re-install the carb or replacement carbs with such.

But:
My original post question is not about that plate.

But thanks for that info also.

[hanz63]

I guess that I'm not following the right path here then. There are specific restrictor plates on the twins too?

[KE4AVB]

I believe what Arkie is referring to are these. Actually they are just gaskets and yes I leave them out.


The swirl plate looks someone took hammer to it and dented it. These are the twin Swirl plates

[KE4AVB]

Also I went the two old Briggs service manual books here and the service bulletins only went into the 600's. So I don't have actual copy here to scan to PDF file.